1. Field of the Invention
The present invention relates to marine vessel propulsion assembly having a thrust bearing.
2. Description of the Related Art
Marine vessel thrust bearings and axial bearings for absorbing propeller thrust are either integrated in a generally known manner in a gearbox or arranged as a free-standing thrust bearing on the propeller shaft, depending on the space requirement and the size of the propulsion system.
Gearboxes may be elastically connected to the marine vessel structure for displacement reasons or in order to damp the introduction of structure-borne sound. In propulsion assemblies having elastically supported gearboxes, it is not possible to integrate a thrust bearing for relatively large propeller thrust forces in the gearbox. In this situation, the thrust bearing must be arranged separately on the propeller shaft. FIG. 4 illustrates an arrangement such as this according to the general prior art.
In FIG. 4 a gearbox 20′ suspended on elastic elements 21′ is connected to a rigidly suspended thrust bearing 23′ by an intermediate shaft 24. This configuration requires a relatively large spacing between the thrust bearing 23′ and the gearbox 20′ to compensate for the displacement of the gearbox 20′ with respect to the thrust bearing 23′ due to deformation of an intermediate shaft 24. The thrust bearing 23′ is arranged in a fixed position. As a rule, the intermediate shaft 24 has a length of several meters, and is linked to the output driveshaft 2′ from the gearbox 20′ by a flanged connection. The intermediate shaft 24 is linked to the thrust bearing 23′ by a further flanged connection, and the propeller side of the thrust bearing 23′ is connected to a propeller shaft 25′.
The arrangement of flexible couplings between the bearing and the gearbox makes it possible to reduce the distance, but the couplings result in a large amount of additional weight and considerable additional costs.
Furthermore, very hard elastically separately suspended thrust bearings are generally known to reduce the conduction of structure-borne sound, and these allow compensation for displacement of the gearbox. The propeller thrust is in this case introduced into the marine vessel structure by elastic damping elements which are arranged in the longitudinal direction of the marine vessel. The disadvantage in this case is that the thrust bearing housing must be supported on the outside by additional, heavy and large damping elements, so that a relatively large distance is required between the bearing and the gearbox here as well.